Since a number of the 227b dust monitors have been alarming with "sensor fail" recently, I've started trying to get the external pump in the mechanical room running again, so that I can use some of the ones that have their internal pumps removed. I had stopped my previous attempts when the pump seemed to be running too hot. So far I have only been able to replace the dust monitor at the H1 PSL (location 10). After going back and forth between the LVEA and the mechanical room to adjust the valve on the pump and check the flow rate at that dust monitor, I got a reading of ~.1 cfm. However, the flow measured at the dust monitor in the H1 electronics racks (location 8) was less than .1 cfm. I do not know why the flows differ and I have left that dust monitor turned off. The flow rate the H1 PSL dust monitor should probably be rechecked. These are the only two currently connected to the external pump. Since I wanted to make sure that there wasn't some unused connection that was not blocked, I traced the hose out in the LVEA as much as I could. Since it was unused, I disconnected and plugged the connection on the hose manifold that led to the previous locations of ISCT 10 and the H2 electronic racks. I have also removed the flow meter from the hose next to the pump in the mechanical room, since I do not trust its readings, and therefore thought there might as well be a clear line there for now. I have also replaced the exhaust filter on the vacuum pump with a tee. The pump seems to be running alright at this point. The valve on the vacuum pump is set so that the gauge reads 350 mmHg VAC.